Engine starter



April 211, 1953 G. w. LEWIS ENGINE STARTER A Filed July 26 1950 INVENTOR. George 14 Lewis Y lwzhgfifzznl Patented Apr. 21, 1953 UNITED STATES PATENT OFFICE 2,635,470 ENGINE STARTER George W. Lewis, Toledo, Ohio Application July 26, 1950, Serial N 0. 176,004

13 Claims. 1

The present invention relates to engine starting apparatus and particularly to an engine starter drive of the automatic yielding type, in which the engine driving member is automatically traversed into and out of mesh with a gear of the engine to be started.

The invention comprehends a starter drive for engines of great simplicity having provisions for accelerating the traversing of the pinion into mesh with the engine gear and effectively cushioning the torque transmission to thereby reduce the noise, as well as the shock and stresses incident to the'engine starting operation.

The invention comprises a very inexpensive and compact starter drive incorporating fully enclosed concentrically mounted threaded members formed with threads of asymmetrical crosssection which are constructed and arranged to provide a substantially uniform radial clearance to thereby decrease their contacting area and a generous spacing between their sides to provide an effective oil film shearing arrangement.

The invention contemplates a starter drive, very quiet in operation, incorporating a member of elastically deformable material which is subjected to both torsion and axial shear during the engine cranking operation and by means of which the concentricity of a loosely coupled threaded connection of reduced area is maintained with respect to the power shaft.

The invention embraces a starter drive of comparatively small outside diameter incorporating provisions for reducing the possibility of the drive locking either in mesh or operating position during engine starting, or in the demesh or idle position after the pinion has been propelled out of engagement when the engine becomes selfoperative.

The invention includes a starter drive provided with a rotatable eccentrically mounted counter-weight frictionally connected to the pinion assembly. The counter-weight provides means for accelerating the longitudinal movement of the pinion toward the engine gear, as well as for preventing rapid longitudinal oscillatory movement of the pinion as the engine passes over its compression points, and for checking pinion rebounds after demeshing.

According to the foregoing summary of the invention indicating its general nature and substance, its main objective is the provision of an engine starter drive wherein the meshing of the pinion with the engine gear is instantaneously obtained, the cranking operation is maintained until the engine is reliably self-operative and wherein rebounding of the pinion after its demeshing operation is prevented as well as the locking of the pinion in meshing or demeshing position is substantially eliminated.

In prior conventional starter drives of the automatic engine meshing and demeshing type, the longitudinal movement of the pinion is se-' cured after the motor has attained considerable velocity and speed due to the friction of the pinion assembly with respect to its mounting and the friction of the threaded connection which provides the longituinal movement of the pinion. Hence, this cumulative friction relatively proe longs the free-running period of the motor. Prolongation of the free-running period of the starter motor, or permitting such period to be of considerable duration, produces a very high kinetic energy of rotation of the motor armature and parts rotated thereby, so that shock and stresses at the initial starting, due to the deceleration torque and the torque of the motor, are of very high magnitude, causing chopping ofthe ringgear teeth as well as those of the pinion. Thus the effective operation of the starter drive, as well as the life of the engine flywheel gear, is materially impaired, causing performance failures after comparatively short periods of use.

The engine starter drive of the invention overcomes the listed drawbacks and performance failures by reducing to a minimum the cumulative objectionable friction referred to and by providing a rotatable eccentrically-mounted counter-weight associated with the pinion assembly for accelerating the longitudinal move-' ment of the pinion, so that the meshingoperation is instantaneously effected upon initial rotation of the motor shaft. In the starter drive of the invention, provisions are included to materially reduce the areas of engagement not only of pinion assembly with respect to the power shaft but also of the threaded connection without introducing friction as would interfere with the longitudinal movement of the pinion in response to smau initial rotary motion of the motor shaft. By these provisions, the free running period of the motor is reduced to a minimum whereby the deceleration torque and kinetic energy of rotation of the motor armature is of exceedingly low value, so that the possibility of chopping of the ring gear teeth as well as those of the'pinion is eliminated.

The invention includes as one of its objects a starter drive incorporating yielding means, ar

ranged to insure quietness and a smoothness in operation with the required flexibility and resilience for application of torque to start the engine and which eliminates the possibility of spring breakage.

An object of the invention is to provide a starter drive incorporating a pinion assembly iournaled directly on a power shaft for movement with respect thereto having provisions for reducing to a minimum the area of contacting engagement therebetween in order to allow freedom for its longitudinal movement on the power shaft without cocking.

Another object of the invention is the provision of a torque transmitting connection having threads of asymmetrical cross-section, so arranged that thread-clutchin actionis'minimized in one side to prevent the sticking of the pinion in its idle position when thrown back by the starting of the engine and where thread-clutching action is discretely cultivated on the pressure side to prevent premature demeshing of the pinion in its operating position.

Another object of the invention :is to provide. in a starter drive, an elastically deformable mem-. ber inthe form of a hollow cylinder of rubber or the like surrounding and bonded to the threaded nut and being wedged or compressed into frictional engagement with the interior of the enclosing housing constituting the sole driving connection between the shaft and pinion. The deformable member is arranged to yield both torsionally and endwise and thereby coacts with a specially formed threaded connection to prevent jamming or sticking of the drive in its operating or idle positions.

Another object of the invention is the provision of an enclosure for a starter drive which not only fully covers the yielding driving and threaded connections but limits and defines the pinion operating position and which precludes the possibility of foreign matter coming into contact with the operative members of the drive to thereby interfere with their proper functions.

A further object of the .invention is to provide a starter drive which is quiet in operation and of reduced outside diameter and of smaller overall dimensions as compared to conventional drives of like torque capacity, the drive comprising a small number of parts of simple and economical construction, highly adaptable for mass production manufacture.

Other objects and advantages of this invention relating to the arrangement, operation and function of the related elements of the structure, to various details of construction, to combinations of parts and to economies of manufacture, will be apparent to those skilled in the art upon consideration of the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Referring to the drawings:

Fig. I is a side elevation, partially in section, showing a form of the invention with the parts in idle position;

Fig. II is a view similar to Fig. I showing the parts thereof in engine cranking or operating position;

Fig. III is an enlarged fragmentary sectional view of the threaded connection of the invention;

Fig. IV is an isometric view of the rotatable inertial mass embodying a feature of the invention;

Fig. V is a sectional view taken along the line 4 VV of Fig. II looking in the direction of the arrows.

The invention may be incorporated in any type of engine starting apparatus and for a practical application of its principles, the invention is shown in the drawings as embodied in an electric starter for internal combustion engines. However, it is to be understood that the invention is not limited to the particular form shown but that it is contemplated to use the same with any suitable prime mover and whenever the invention or its components may be found to be of utility.

Referring to the drawings, in the embodiment illustrated, the prime mover is shown in the form of an electric motor In preferably of the series type. The motor II) operates the power driven shaft which is shown as an extended armature shaft I2 journaled on a suitable bearing I3 carried by the flanged end plate I4, by means of which the motor and the drive of the invention are attached to the engine block not shown. As illustrated in Figs. I and II, the starter drive is a selfcontained unit having an enclosing housing or barrel I5 fixed to the power shaft I2 by suitable means. A key I6 and a set screw I! carried by the hub or collar I8 of the barrel I5 rigidly secures the starter drive as a unit on the shaft I2 locating the engine driving member or pinion 20 in a position to be automatically moved into and out of meshing engagement with a member of the engine to be started such as a flywheel ring gear 2!.

The means of the invention to effect the automatic engagement of the starter drive with the engine to be started upon initial rotation of the starter motor I0 includes a concentrically supported, loosely-coupled, inclined, torque-transmitting connection of reduced area of engagement, providing a longitudinal component for traversing the pinion 20 axially of the power shaft I2. The loosely-coupled, helical connection of reduced area is provided to enhance the speed of the meshing operation of the pinion, preventing sticking to relative motion under dirty or oily starting conditions during cold weather. In the embodiment shown, the torque transmitting connection of the invention is formed on the outer surface of the pinion actuator or hollow screw shaft 23 connected to the pinion extension 24 and on the bore or internal surface of the controlled head or driving nut 25 piloted by the barrel I5 in cgncentric relation with the power driven shaft The torque-transmitting connection of the invention, as shown in Figs. I and III, comprises male type screw threads 26 of asymmetrical cross-section having non-symmetrical sides 21 and 28 formed on the outer surface of the pinion actuator 23 for cooperative engagement with internal screw threads 29 of asymmetrical crosssection having corresponding non-symmetrical sides 30 and 3| formed on a portion of the bore of the control head 25. The threads 25 and 29 are preferably of the triple screw type, being formed and correlated for concentric relation to provide generous spacing between their sides and a liberal thread-crest-clearance or a substantially uniform radial spacing between their major and minor diameters over conventional maximum tolerances.

As shown in Fig. I, the power driven shaft I2 has a portion of reduced diameter 32 and the bore of the pinion and its sleeve 24 is enlarged as at 33, so that in non-operating position, the area of engagement between the pinion and shaft is greatly reduced to prevent resistance to rein..-

tive axial movement therebetween. The pinion sleeve 24 has its end telescopically splined to the actuator 23 which is directly mounted on the shaft l2. To reduce friction of the actuator 23 on shaft l2, and provide the concentric relation for the loosely-coupled connection 2629, the bore 34 of the actuator 23 has four bearing segments or lugs 35 of narrow radial width formed to directly engage shaft [2. The right angle positioned lugs 35 have a sliding fit on the longitudinal slots 36 formed at the end of th pinion sleeve 24, the outer surface of which, in turn, snugly fits the bore 34 of the actuator, the slots 36 are closed by a snap ring 31. Thus the pinion and its actuator, which form the pinion assembly, have a very reduced area of contacting engagement with the power shaft, and are arranged to allow maximum freedom for longitudinal movement on the power shaft without cooking of pinion.

The driving nut 25 is piloted and connected to the barrel 1 in concentric relation to shaft l2 by the yielding means of the invention which constitute the sole driving connection between the starter pinion 20 and the power shaft l2 arranged to yield both torsionally and endwise and which in turn maintain the concentricity of the threaded connection 26-2 9. The yielding means are shown as a tubular body or hollow member 40 of elastically deformable material interposed between the barrel l5 and nut 25 having tractive connections with each of said members. In the preferred form of the invention the tractive connection between the member 40 and the driving nut 25 is in the form of a bond which can be obtained by vulcanizing its central surfac 4! to the outside surface 42 of the nut 25. The tractive connection between the member 40 and the barrel i5 is established by compressing or wedging the member 40 while inserting the same within the barrel to obtain by its reflex expansible force an effective frictional driving connection between its outer surface 43 with the interior surface 45 of the barrel. The tubular member 40 is preferably made of rubber or a synthetic material which provides substantially the same characteristics of rubber with respect to compressability and elasticity and is so dimensioned with respect to the barrel and driving nut that the tractive connections outlined can be effectively carried out.

The starter pinion 20 and its actuator 23 as herein before described have a telescopic splined connection which provides rotation together and limited longitudinal motion therebetween. In order to hold the pinion 2i] and its actuator 23 normally in extended position to permit a, yielding backward movement a resilient member is provided such as a spring 41 surrounding the sleeve section 24 of the pinion. The spring 41 is assembled under an initial preload by being interposed between the forward end of the driving screw 23 and rear surface of the rotatable eccentric inertial mass 50 of the invention which thereby urges into frictional engagement its front surface with the non-working ends 52 of the chamfered teeth 53 of the pinion 20. This arrangement provides a very simple longitudinal yielding connection to effect the meshing of the pinion 20 and flywheel ring gear 2| in case the chamfered teeth 53 of the pinion and those of the engine ring gear meet end to end during the shifting operation.

The provision of a rotatable and. slidable iner-. tial mass associated with the pinion constitute one of the important features of the invention because this mass is arranged to operate in the following three-fold manner: First, as means to accelerate the meshing of the pinion with the engine gear upon initial rotation of the motor shaft; second, as means which produce a radial force imposing resistance to the endwise movement of the pinion, reducing thereby pumping and backout of mesh of the pinion during the cranking operation; and, third, as means to synchronize the pinion with the armature shaft to resist pinion rebounds on the demeshing operation.

In the embodiment shown, the inertia mass of the invention is in the form of a detachable disclike weight 50 having its greatest thickness at one side of its axis of rotation whereby the same is overbalanced. The weight 50 is provided with an opening 5|, located at a point offset from its center of mass, to loosely fit the outer surface of the pinion sleeve 24 so that the same is mounted for rotation thereon. The inertia mass 50 is journalled and frictionally urged as well as resiliently slidable on the pinion sleeve by having its front surface 54 in frictional engagement with the nonworking ends 52 of the pinion teeth 53 by a coil spring 41. The coil spring, as hereinbefore described, is assembled with an initial preload between the driving screw 23 and the rear surface 56 of the inertial mass 50. The coaction and cooperative relationships by which the frictionally rotatable and resiliently slidable eccentrically mounted inertial mass 50 functions in the threefold manner specified will be found in the description of the operation.

An anti-creeping spring 58 surrounding the shaft I2 is arranged to bear at one end against the outer surface of the power shaft bearing l3 and at its other end against the pinion 20. This arrangement provides sufficient frictional resistance to prevent the possibility of rotary movement of the pinion 20 on power shaft 12 due to vibration. This not only holds pinion 20 in its home or retracted position, but aids in the shifting of the pinion the instant the power shaft l2 rotates.

According to the present invention means are provided to prevent the sticking or binding of the starter pinion in its idle position when thrown back by the starting of the engine. As particularly shown in Fig. III this means comprises the formation of the non-pressure sides 21 and 3| respectively of each of the threads 26 and 29 almost vertical or at an angle A ranging between 0 to 15 degrees, so that the thread clutching action of the non-pressure side is greatly reduced. In addition by forming the driving or pressure sides 28 and 30 respectively of each of the threads 26 and 29 inclined forming a larger angle B ranging between 30 to degrees from planes perpendicular to the axis of rotation, the thread-clutching action of the special threaded connection of the invention is discretely cultivated to prevent objectionable pumping or rapid longitudinal oscillatory movement of the pinion as the engine passes its compression points or when torque fluctuations take place, as well as premature demeshing of the pinion in case the engine attempts to becom self-operative but fails and stops. Moreover, the thread-clutching action of the inclined or pressure side of the threads coacts with the eccentric rotatable inertial mass 50 to maintain the pinion 20 in mesh with the engine ring gear 2| until the engine is reliably self-operative.

I have found that the invention can be e1- i'ectively carried into practice by forming the pressure side 28 and 30 respectively of the threaded connection 2629 at an angle of approximately 30 degrees with the vertical, while the non-pressure side 21 and 3| respectively of said connection is formed at an angle of 5 degrees with the vertical so that the overall angle between the sides of each thread is 35 degrees. However, it is understood that the objectives of the invention are realized by the angularity specified for the pressure and non-pressure sides of the threaded connection as the thread-clutching action for each side is properly controlled.

The advantages that can be secured by providing each side of the threads 26 and 29 with a different degree of thread clutching action are materially enhanced by the provisions of the invention used to reduce their frictional area of engagement. The reduction of the friction of the limited area of engagement of the threads 26 and 29 is predominantly manifested in their idle position because the length of their mutual engagement is then shorter than when in operating or engine cranking position. This is clearly seen by a comparison of Figs. I and II. The reduction of friction and limitation of the area of engagement of the threads 26 and 29 is readily obtained as hereinbefore described by the liberal thread-crest clearance which may take the form of a 34 radial spacing between the major and minor thread diameters, as well as by the fact that the threads are formed and correlated to provide a generous longitudinal spacing therebetween.

The operation of the engine starter of the invention may be summarized as follows: starting the cycle of operation with the parts in the position shown in Fig. I, the energization of the motor l causes the rotation of the power shaft |2 with barrel I5, member 40 and drive nut 25 which is transmitted through the loosely-coupled threaded connection 2629 to the control member 23 and thereby to the starter pinion 20. Upon the initial rotation of the power shaft l2, the rotation of the pinion 20 is substantially prevented or checked owing to its inertia and that of rotatable, weighted member 50 which in turn imposes frictional resistance to the turning of the pinion in addition to that of the anticreeping spring 58. The coaction of the rotata-ble weighted 50 with the pinion assembly renders immediately effective the longitudinal component of the torque-transmitting connection 26-29 to'accelerate the meshing of the pinion 20 with the engine ring gear 2| upon the initial rotation of the power shaft l2. Due to the limited area of contact to the pinion assembly with the power shaft |2, as well as the reduced area of contacting engagement of the threads 26 and 28, the pinion 20 is propelled into engagement with the ring gear 2| before the power shaft l2 attains considerable velocity and speed.

In case of interference with the propulsion of the pinion 20 to its engine-meshing position, such as tooth abutment with the ring gear teeth, the driven screw 23 will continue to move axially and the thrust is absorbed by the spring 41 through the lost motion connection between the pinion 20 and screw member 23. Such interfering action initiates the transmission of torque from the barrel l to the pinion 20 subjecting the elastic deformable member 40 to torsion .to turn the pinion bringing its chamfered teeth 53' into registration with those of the engine ring gear 2|. Consequently, the expansive force of 8 the spring 41 quickly meshes the pinion 20 with the engine rin gear 2|.

The full meshing engagement of the pinion 20 with the engine ring gear 2 I, as shown in Fig. II. is defined by the abutting engagement of the control screw 23 with the stop or thrust washer 46 closing the open end of the barrel |5 held in the groove 48 by a retainer ring 49. This engagement will stop further longitudinal movement of the pinion 20 toward the engine gear 2| and initiate the gradual transmission of torque to the pinion to crank the engine. The load of turning the engine will be manifested by a torsional and a longitudinal component in the reverse direction caused by the screw jack action of the concentric loosely-coupled threaded connection 2629 causing the driving head 25 to move rearwardly subjecting the member 40 to axial shear. Thus the turning force to crank the engine is transmitted from the starting motor to the pinion in a yielding manner by the torsion and axial shear of the member 40 caused by the relative rotation and axial movement of the head 25 with respect to the barrel l5.

During the engine cranking operation, the inertial mass 50 rotates with the pinion 20 and the frictional contact of the bore of the inertial mass with the sleeve of the pinion is added to the frictional contact of the inertial mass with the non-working side 52 of the pinion teeth 53 caused by the spring member 41. Moreover, due to the fact that the inertial mass 50 has its center of mass displaced from the center of rotation, the radial force developed by centrifugal action imposes a radial load on the pinion which is proportional to the square of the velocity of the inertial mass. The combined action of the frictional resistance, due to the plural contacting surfaces of the inertial mass with the pinion, and the radial load imposed on the pinion by the inertial mass, operate as means to check relative rotation between the pinion and inertial mass. Therefore, any change in the speed of the engine member is resisted by the kinetic energy of rotation or the rotational inertia of the inertial mass 50. Moreover, the cumulative effect of the frictional resistance, radial load, and rotational inertia of the inertial mass operate, when the engine overruns the speed of the pinion or fluctuations of the torque transmitted takes place, to check the screw jack action of threaded connection 2629, opposing thereby premature demeshing or axial movement of the pinion with respect to the engine flywheel, thus counteracting any pumping action of the pinion with respect to the engine ring gear. The coaction of the rotatable inertial mass 50 with the discreet utilization of the thread-clutching action on the pressure side of the threads 26 and 29, further prevents objectionable longitudinal oscillatory movement of the pinion and its premature disengagement in case of false starts.

The instant the engine fires and begins to rotate by its own power the driving nut 25 is turned rapidly with respect to the barrel l5 by the release of the torsion imposed by the engine load on the yielding member 40. This rapid angular movement of the driving nut 25 is very effective in preventing the jamming or sticking of the pinion in its operating position in view of the fact that the only surfaces in contacting engagement of the threaded connection 25-20 are their respective pressure sides 28 and 30.

When the engine starts under its own power, the acceleration of. the engine ring gear 2| imparts to the pinion 20 a rate of rotation in excess of that of motor shaft I2 and thereby the pinion 20 will be screwed out of meshing engagement with the ring gear 2| being thereby axially moved to its idle position until the end of the pinion sleeve '24 engages the loosely-mounted, steel washer 6i! abutting the hub member l8 of the barrel. During the demeshing operation, the eccentrically-mounted inertial mass 50 acquires high velocity, and the energy stored thereby is dissipated by its action on the pinion assembly and particularly by its friction against the nonworking side 52 of the pinion teeth 53 synchronizing the rotation of the pinion with that of the armature or power shaft l2. This synchronizing action of the inertial mass 50 effectively resists any reverse movement of the pinion 20 toward the engine ring gear 2| and substantially eliminates pinion rebounds. Upon the operation of the engine under its own power the parts will take the positions shown in Fig. I after the motor is deenergized, so that the cycle of operation can be eifectively repeated.

In the starting mechanism described the barrel I and its closing member 46 form an enclosure which not only limit and define the pinion operating position insuring the concentricity of the loosely threaded connection 2629 but in addition precludes dust and foreign matter to interfere with operative members of the drive so that the drive operates successfully under adverse conditions. In this connection it should be noted that drive must operate in cold weather when subjected to dirty, wet and oily starting conditions. Under such conditions the oil film between relatively movable elements such as the power shaft and pinion congeals restraining their movement and therefore must be broken up to insure the advance of the pinion into mesh with the engine gear. The provisions of the invention which reduce the area of engagement of the pinion 20 and its actuator 23 with the power shaft 12 provide an effective oil film shearing arrangement.

It should be noted that the possibility of sticking or binding of the coacting demeshing sides 21 and 3| of the threaded connection in the idle position of the pinion, when the same is propelled out of engagement by the starting of the engine, is substantially prevented as their thread-clutching action is substantially lessened.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of being practiced and carried out in various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed for purposes of description and not limitation, and it is not intended to limit the scope of the following claims beyond the requirements of the prior art.

-What is claimed:

1. An engine starter drive including a power shaft, a hollow member rigid with said shaft, a

threaded nut, a tubular body of elastically deform-able material having a tractive connection with said hollow member and threaded nut, a

shifting and control screw in threaded engagement with said threaded nut directly mounted on said power shaft having a limited area of engagement therewith, a starter pinion directly mounted on said power shaft and being actu ated by said control screw for engaging and cranking a member of the engine to be started, the pinion and shaft having a limited area of contacting engagement, 9, splined connection between said starter pinion and control screw providing positive rotary motion together and longitudinal lost motion therebetween, stop mean carried by said hollow member arranged for engagement with the control screw when the starter pinion reaches a position for adequate engagement with the engine member, a rotatable counter-weight frictionally connected to said pinion and resilient means arranged to provide said frictional connection between the counter-weight and pinion to increase the inertia of the pinion and thereby enhance the longitudinal component of said threaded connection I01 accelerating the engagement of the starter pinion with the engine member upon the initial 1101335101]. 011 Sada. POWBI' shaft.

2. An engine starter drive including a power driven shalt, a pinion directly ournaled on the shaft for longitudinal movement with respect{ thereto and for rotary movement therewith to engage and crank a member of the engine to be started, coactmg provisions on said power shaft and pinion for reducing their area of engagement, a torque transmitting connection formed or interengaging helical splines of asymmetrical cross-section interposed between said pinion and power shaft for driving said pinion by said shaft,

said helical splines being formed and arranged to reduce their area of engagement, a rotatable counterweight eccentricaiiy mounted for longitudinal movement With H18 P1111011 and I OI I'OUHP tion with respect thereto, resilient means for urging said counterweight in irictional engagement with said pinion and a body of elastically deformable material having tractive driving connections with the power shaIt and the torquetransmitting connection and arranged therewith threaded on said member, a barrel fixed to the shaft, 2. rubber annulus radially compressed to provide a secure frictional connection between its outer surface and the inner surface of the barrel and inner surface of the rubber annulus bonded to said nut whereby the rubber annulus forms the sole driving connection between the barrel and nut so that endwise motion of the nut away from the pinion and relative circumferential motion of said nut relative to said barrel is yieldingly permitted when torque is transmitted to the ring gear.

fl. An engine starter drive including a power driven shaft, a barrel rigid with said shaft to rotate therewith, a threaded nut, a tubular body 0f elastically deformable material bonded to the threaded nut and compressed into frictional engagement w th the barrel, a control screw journa-led on said shaft and being loosely coupled with said threaded nut to decrease friction therebetween, a starter pinion freely journaled on the shaft for engaging and cranking a member of the engine to be started, a connection between said starter pinion and control screw providing positive rotary motion together and longitudinal lost motion therebetween, stop means arranged to be engaged by the control screw when the starter pinion reaches a position for adequate engagement with the engine member, and a rotatable eccentric inertial mas frictionally contacting the pinion for increasing its inertia and the effect of the longitudinal component of the threaded connection of said nut and control screw for accelerating the engagement of the starter pinion with the engine member upon the initial rotation of said power driven shaft.

5. In a starter for transmitting starting torque to the ring gear of an engine, a, power driven shaft, a pinion directly mounted on the shaft, means on said pinion and shaft for reducing their engaging area to facilitate the meshing of the pinion with the engine ring gear, a. threaded member connected to said pinion and having a limited area of engagement with the shaft, a nut member threaded on said member, a barrel fixed to the shaft, a rubber member adapted to be compressed to provide a tractive frictional connection between the barrel and the rubber member and being bonded to said nut constituting the sole driving connection between the barrel and nut so that endwise motion of the nut away from the pinion and relative circumferential motion of said nut relative to said barrel is permitted when torque is transmitted to the ring gear.

6. In a starter for engines, a barrel operated by a power driven shaft, a starter pinion mounted on the shaft for longitudinal movement with respect thereto and for rotary movement therewith to engage and crank a member of the engine to be started, a loosely-coupled screw-threaded torque-transmitting connection having its pressure side of different angularity than its other side, said connection being splined at one end to said pinion and being arranged to reduce the resistance to the longitudinal movement of the pinion toward the engine member upon the initial rotation of the shaft and for maintaining an operative connection of the pinion with the engine member until the engine is reliably selfoperative, an elastically deformable member having tractive connections with the barrel and with the other end of said threaded connection, said deformable member adapted to yield both torsionally and endwise constituting the sole driving connection between the barrel operated by power shaft and threaded connection, and an inertial weight frictionally and eccentrically mounted on the pinion for rotation with respect thereto.

7. An engine starter drive including a power driven shaft, a driving member mounted on said power shaft for rotary and longitudinal movement with respect thereto, an externally threaded sleeve having threads of asymmetrical crosssection mounted for movement on said shaft for transmitting to said driving member rotary and longitudinal movement to engage and to crank a member of the engine to be started, a barrel fixed to said shaft, a threaded nut member having threads of asymmetrical cross-section for engagement with those of said sleeve, elastically deformable means having driving connections with said barrel and said nut member to yield torsionally and endwise under torque transmission from said shaft to the driving member, and a rotatable counterweight frictionally connected to said driving member to increase its inertia and thereby enhance the longitudinal component of the threaded connection of said nut and sleeve for facilitating the engagement of said driving 12 member with the engine member upon the initial rotation of said shaft.

8. An engine starter drive including a power driven shaft, a barrel rigid with said shaft to rotate therewith, a threaded nut, a tubular body of elastically deformable material bonded to the threaded nut and compressed into frictional engagement with the barrel, a control screw journaled on said shaft having spaced sections of limited area to decrease friction therebetween, a starter pinion journaled on the shaft having an enlarged bore section to reduce friction therebetween, a connection between said starter pinion and control screw providing positive rotary motion together and longitudinal lost motion therebetween, and stop means arranged to be engaged by the control screw when the starter pinion reaches a position for adequate engagement with the engine member.

9. An engine starter drive including a power driven shaft, a pinion directly journaled on the shaft for longitudinal movement with respect thereto and for rotary movement therewith to engage and crank a member operatively connected to the engine to be started, provisions on said pinion and power shaft for reducing their area of engagement to reduce the resistance to the longitudinal movement of the pinion toward the engine member upon the initial rotation of the power driven shaft, a torque transmitting connection interposed between said pinion and power driven shaft for driving said pinion by said shaft, said torque transmitting connection comprising interengaging helical splines having a liberal crest clearance and a generous spacing between their coacting sides, and a rotatable counterweight eccentrically and frictionally mounted on the pinion for longitudinal movement with the pinion and for rotation with respect thereto.

10. An engine starter drive including a, member operated by a power driven shaft, a pinion directly journaled on the shaft for longitudinal movement with respect thereto and for rotary movement therewith to engage and crank a member of the engine to be started, provisions on said power shaft for decreasing the area of engagement of pinion with the shaft to reduce the resistance to the longitudinal movement of the pinion toward the engine member upon the initial rotation of the power driven shaft, a torque transmitting connection formed of interengaging helical splines of asymmetrical cross-section having tractive driving connections between said pinion and the member operated by the power driven shaft for driving said pinion by said shaft. a rotatable mass eccentrically mounted for frictional engagement and relative rotation with said pinion, and a body of elastically deformable material having tractive driving connections with the member operated by the power shaft and with the torque transmitting connection, said deformable body arranged to be subjected to both torsion and longitudinal shear during the cranking operation.

ll. In an engine starter drive a power shaft, a pinion slidably journaled thereon for engagement with an engine member, means including loosely coupled interthreaded members for traversing and rotating the pinion, means for mounting the outwardly positioned and internally threaded of said members in concentric relation with the axis of rotation of the shaft comprising spaced cylindrical surfaces connected respectively to one of said members and the power 13 shaft, and a ring of elastically deformable material having interiorly and exteriorly tractive connections with said cylindrical surfaces and being subjected to torsion and axial shear when torque is transmitted from the power shaft to pinion to start the engine.

12. In a starter for transmitting starting torque to the ring gear of an engine, a power driven shaft, a pinion rotatable on the shaft and slidable endwise thereon into mesh with the engine ring gear, means on said shaft for reducing its area of engagement with the pinion and thereby decrease friction therebetween when relative movement takes place, a threaded actuator connected to said pinion having symmetrically spaced sections engaging said shaft to reduce their area of engagement and thereby decrease the frictional resistance for relative movement therebetween, a driving nut loosely threaded on said actuator providing a liberal uniform radial space between the respective major and minor diameters of their coacting threads for forming a loosely coupled driving connection of reduced area, a hollow member afiixed to said shaft, elastic means connecting said hollow member and driving nut, and said elastic means being enclosed by said hollow member and thereby forming the sole driving connection between the hollow member and nut so that any endwise movement and relative circumferential motion of said nut relative to said hollow member is yieldingly permitted when torque is being transmitted from the power shaft to the ring gear.

13. In a starter for transmitting starting torque to the ring gear of an engine, a power driven shaft, a pinion mounted for rotation on said shaft and slidable endwise thereon into mesh with the engine ring gear, a reduced portion formed on said shaft for decreasing its area of engagement with the pinion and thereby minimize friction therebetween when relative movement takes place, a control screw non-rotatably connected to said pinion, said control screw formed with sections of reduced area engaging said shaft to thereby minimize the frictional resistance for relative movement therebetween, a driving nut loosely threaded on said control screw providing a generous longitudina1 spacing between the sides of their co-acting threads for forming a loosely coupled torque-transmitting connection of reduced area, a barrel non-rotatably connected to said shaft, a yielding member surrounded by said barrel, and tractive driving connections for connecting said yielding member with said barrel and driving nut whereby said member yieldingly takes up both endwise and circumferential motion of said nut with respect to said barrel when torque is being transmitted from the power shaft to the engine ring gear.

GEORGE W. LEWIS.

References Cited in the file of this patent UNITED STATES PATENTS Sekella Mar. 18, 1941 

